Figure 1

Recognition of microbial RNA and DNA by endosomal Toll-like receptors (TLRs). TLR9, TLR7 (and TLR8), and TLR3 recognize CpG DNA, single-stranded RNA (ssRNA), and double-stranded RNA (dsRNA), respectively. TLR9 and TLR7/8 signal through a Toll-interleukin-1 receptor- (TIR-) containing adaptor molecule MyD88, whereas TLR3 signals exclusively through a different adaptor, TRIF. MyD88 and TRIF induce the expression of genes for type I interferons and pro-inflammatory cytokines by activating transcription factors of the IRF and NFκB families. DD, death domain; IRF, interferon response factor; LRR, leucine-rich repeat; NF, nuclear factor; SHIM, RIP homotypic interaction motif.